US President Donald Trump will not invoke executive privilege to block former FBI director James Comey's scheduled testimony before Congress this week, the White House said this evening.

"In order to facilitate a swift and thorough examination of the facts sought by the Senate Intelligence Committee, President Trump will not assert executive privilege regarding James Comey's scheduled testimony," White House spokeswoman Sarah Sanders told reporters.

Mr Comey was leading a Federal Bureau of Investigation probe into alleged Russian meddling in last year's US presidential election and possible collusion by Mr Trump's campaign when the president fired him last month.

Presidents can assert executive privilege to prevent government employees from sharing information.

If Mr Trump had asserted executive privilege over Mr Comey, it would have likely created the perception that the administration was seeking to hide information about the FBI's Russia investigation.

It has been reported that Mr Comey plans to talk about conversations in which Mr Trump pressured him to drop his investigation into former national security advisor Mike Flynn, who was fired for failing to disclose conversations with Russian officials.

Mr Comey is scheduled to testify for the first time since his firing before the Senate Intelligence Committee as part of the committee's Russia-related investigation.